In a millimeter-wave wireless communication system, the high-frequency signal source is a very important component. For instance, radar and communication systems require oscillators to provide high-frequency signals.
In prior art, the method of designing high-frequency oscillators is to use fundamental oscillators. However, when used in designing a high-frequency signal source, this method has the drawbacks of low transistor gain and low resonator quality factor (Q factor). Therefore, fundamental oscillators must be matched with frequency multipliers to provide a high-frequency signal. The oscillator of this configuration is designed to resonate at lower frequency of the output signal. Therefore, higher transistor gain and larger resonator Q factor can be obtained. However, amplifiers and filters usually are needed for oscillators of this configuration, hence resulting in large circuit area.
To overcome the drawbacks but maintain the original advantages of the fundamental oscillators, a push-push oscillator configuration has been proposed. The push-push oscillator combines two fundamental oscillators so that when the fundamentals are out of phase, the second harmonics will be in phase. Therefore, the in-phase second harmonics will combine at the output terminal, while the anti-phase fundamentals will cancel out each other. Using this configuration, the drawbacks of insufficient gain and low resonator Q factor of fundamental oscillators in high frequency range and the drawback of too large circuit area of fundamental oscillators combined with frequency multipliers can be resolved simultaneously.
The present invention aims to provide a multiple-push oscillator, which can resolve the drawbacks of insufficient gain and low resonator Q factor more easily than a fundamental oscillator or a push-push oscillator does.